Torque fluctuation absorber

ABSTRACT

A torque fluctuation absorber includes a first plate member to which power of rotation is transmitted from a first rotational shaft, a second plate member arranged at a preset distance from the first plate member, a third plate member arranged between the first plate member and the second plate member and configured to transmit power of rotation to a second rotational shaft. The torque fluctuation absorber also includes a fourth plate member arranged at a preset distance from the second plate member, and a resilient member arranged between the second plate member and the fourth plate member and configured to bias the second plate member towards the third plate member. The fourth plate member includes a fulcrum point that supports a mid portion of the resilient member.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 U.S.C. §119 toJapanese Patent Application No. 2009-074051 filed on Mar. 25, 2009, theentire content of which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to a torque fluctuation absorber that takes uptorque fluctuations between rotational shafts. More particularly, itrelates to a torque fluctuation absorber having a limiter unit thatproduces slip when the fluctuating torque has reached a preset value.

BACKGROUND DISCUSSION

A torque fluctuation absorber is arranged e.g. on a power transmissionpath between an engine and a motor in e.g. a hybrid car to absorb orsuppress the torque fluctuations caused in the engine and the motor. Thetorque fluctuation absorber may include a damper unit that takes up thetorque fluctuations by a spring force, a hysteresis unit that absorbs orsuppresses the torque fluctuations by the hysteresis torque caused byfriction, and a limiter unit. The limiter unit produces slip when thetorsion of the rotational shafts may no longer be taken up by the damperunit or the hysteresis unit.

The limiter unit is composed of a friction material sandwiched betweentwo plates. One of the plates is non-rotatable and axially movable withrespect to the other. One of the plates is biased towards the frictionmaterial by a conical spring (see Patent Publication 1, for example).The conical spring is arranged as a continuous annular member, and isinclined from an inner peripheral side towards an outer peripheral side.

[Patent Document] [Patent Document 1]

JP 2005-127507A (FIG. 2)

The entire disclosures of the above-mentioned Patent Document 1 areincorporated herein by reference thereto. An analysis by the presentdisclosure will be given below.

The conical spring has an inner peripheral end abutted against a plate,while having an outer peripheral end supported by another plate. Theinner peripheral end of the conical spring abuts against the formerplate at a location substantially in register with a friction surfacebetween a friction material and the former plate. As a result, thediameter of the conical spring is increased to elevate the cost of theconical spring and hence that of the entire device. The process ofproducing the conical spring is time-consuming. Moreover, the springsteel, as a material for the conical spring, is costly as compared togeneral steel material, thus elevating the cost of the conical springand hence that of the entire device. In addition, the portion of thematerial located more radially inwardly than the inner peripheral end ofthe conical spring is discarded in the production step because of thelarger inner diameter of the conical spring. Hence, the manufactureyield is low, with the result that the cost of the conical spring andhence that of the entire device are increased.

Accordingly, there is a need for a torque fluctuation absorber that maybe produced at a reduced cost.

SUMMARY

In a first aspect, there is provided a torque fluctuation absorbercomprising a first plate member to which power of rotation istransmitted from a first rotational shaft, a second plate memberarranged at a preset distance from the first plate member, a third platemember arranged between the first and second plate members andconfigured to transmit power of rotation to a second rotational shaft, afourth plate member arranged at a preset distance from the second platemember. The torque fluctuation absorber further comprises a resilientmember arranged between the second plate member and the fourth platemember and configured to bias the second plate member towards the thirdplate member. At least one of the second plate member and the fourthplate member includes a fulcrum point that supports a mid portion of theresilient member.

In a second aspect, there is provided a torque fluctuation absorber,comprising: a first plate member to which power of rotation istransmitted from a first rotational shaft; a second plate memberarranged at a preset distance from the first plate member; a third platemember arranged between the first and second plate members andconfigured to transmit power of rotation to a second rotational shaft;and a fourth plate member arranged at a preset distance from the secondplate member. The torque fluctuation absorber further comprises aresilient member arranged between the second plate member and the fourthplate member and configured to bias the second plate member towards thethird plate member. The resilient member includes a first end located ata position having a preset distance from a center of rotation of thefirst rotational shaft and a second end located at a position moreclosely to the center of rotation of the first rotational shaft than thefirst end. The first end abuts against the second plate member in anarea where the second plate member faces the third plate member in theaxial direction. The second end abuts against the fourth plate member.

In a third aspect, there is provided a torque fluctuation absorber,comprising: a first plate member to which the power of rotation istransmitted from a first rotational shaft; a second plate memberarranged at a preset distance from the first plate member; a third platemember arranged between the first and second plate members andconfigured to transmit the power of rotation to a second rotationalshaft; and a sheet spring biasing the second plate member towards thethird plate member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a radial partial cross-sectional view schematically showingthe structure of a torque fluctuation absorber according to Example 1 ofthe present disclosure.

FIG. 2 is an enlarged radial partial cross-sectional view schematicallyshowing the structure of a limiter unit in the torque fluctuationabsorber according to Example 1 of the present disclosure.

FIG. 3 is an enlarged radial partial cross-sectional view schematicallyshowing the structure of a limiter unit in a torque fluctuation absorberaccording to Example 2 of the present disclosure.

FIG. 4 is an enlarged radial partial cross-sectional view schematicallyshowing the structure of the limiter unit in the torque fluctuationabsorber according to Example 2 of the present disclosure.

FIG. 5 left and right are enlarged radial partial cross-sectional viewsschematically showing the structure of a limiter unit in a torquefluctuation absorber according to Example 3 of the present disclosure,and showing the limiter unit before and after assemblage to a flywheel,respectively.

FIG. 6 is an enlarged radial partial cross-sectional view schematicallyshowing the structure of a limiter unit in a torque fluctuation absorberaccording to Example 4 of the present disclosure.

FIG. 7 is an enlarged radial partial cross-sectional view schematicallyshowing the structure of a limiter unit in a torque fluctuation absorberaccording to Example 5 of the present disclosure.

FIG. 8 is an enlarged radial partial cross-sectional view, correspondingto a cross-section taken along line X-X′ of FIGS. 9 and 10, andschematically showing the structure of a limiter unit in a torquefluctuation absorber according to Example 6 of the present disclosure.

FIG. 9 is a plan view schematically showing the structure of a pressureplate of the limiter unit in the torque fluctuation absorber accordingto Example 6 of the present disclosure.

FIG. 10 is an enlarged radial partial cross-sectional view,corresponding to a cross-section taken along line Y-Y′ of FIGS. 8 and 9,and schematically showing the structure of the limiter unit in thetorque fluctuation absorber according to Example 6 of the presentdisclosure.

FIG. 11 is an enlarged radial partial cross-sectional view schematicallyshowing the structure of the limiter unit in the torque fluctuationabsorber according to Example 6 of the present disclosure.

FIG. 12 is an enlarged radial partial cross-sectional view,corresponding to a cross-section taken along line X-X′ of FIGS. 13 and14, and schematically showing the structure of a limiter unit in atorque fluctuation absorber according to Example 7 of the presentdisclosure.

FIG. 13 is a plan view schematically showing the structure of a pressureplate of the limiter unit in a torque fluctuation absorber according toExample 7 of the present disclosure.

FIG. 14 is an enlarged radial partial cross-sectional view,corresponding to a cross-section taken along line Y-Y′ of FIGS. 12 and13, and schematically showing the structure of the limiter unit in thetorque fluctuation absorber according to Example 7 of the presentdisclosure.

FIG. 15 is an enlarged radial partial cross-sectional view,corresponding to a cross-section taken along line X-X′ of FIGS. 16 and17, and schematically showing the structure of a limiter unit in atorque fluctuation absorber according to Example 8 of the presentdisclosure.

FIG. 16 is a plan view schematically showing the structure of a pressureplate of the limiter unit in the torque fluctuation absorber accordingto Example 8 of the present disclosure.

FIG. 17 is an enlarged radial partial cross-sectional view,corresponding to a cross-section taken along line Y-Y′ of FIGS. 15 and16, and schematically showing the structure of the limiter unit in thetorque fluctuation absorber according to Example 8 of the presentdisclosure.

FIG. 18 is an enlarged radial partial cross-sectional view,corresponding to a cross-section taken along line X-X′ of FIGS. 19 and20, and schematically showing the structure of a limiter unit in atorque fluctuation absorber according to Example 9 of the presentdisclosure.

FIG. 19 is a plan view schematically showing the structure of a pressureplate of the limiter unit in the torque fluctuation absorber accordingto Example 9 of the present disclosure.

FIG. 20 is an enlarged radial partial cross-sectional view,corresponding to a cross-section taken along line Y-Y′ of FIGS. 18 and19, and schematically showing the structure of the limiter unit in thetorque fluctuation absorber according to Example 9 of the presentdisclosure.

FIG. 21 is an enlarged radial partial cross-sectional view,corresponding to a cross-section taken along line X-X′ of FIG. 22, andschematically showing the structure of a limiter unit in a torquefluctuation absorber according to Example 10 of the present disclosure.

FIG. 22 is a plan view schematically showing the structure of a pressureplate of the limiter unit in the torque fluctuation absorber accordingto Example 10 of the present disclosure.

FIG. 23 is an enlarged radial partial cross-sectional view schematicallyshowing the structure of a limiter unit in a torque fluctuation absorberaccording to Example 11 of the present disclosure.

FIG. 24 left and right are enlarged radial partial cross-sectional viewsschematically showing the structure of a conical spring of a limiterunit, during and after manufacture, in a torque fluctuation absorberaccording to Example 12 of the present disclosure, respectively.

FIG. 25 is an enlarged radial partial cross-sectional view schematicallyshowing the structure of a conical spring of the limiter unit in thetorque fluctuation absorber according to Example 12 of the presentdisclosure.

FIG. 26 is an enlarged radial partial cross-sectional view,corresponding to a cross-section taken along line X-X′ of FIG. 27, andschematically showing the structure of a limiter unit in a torquefluctuation absorber according to Example 13 of the present disclosure.

FIG. 27 is an enlarged radial partial cross-sectional view,corresponding to a cross-section taken along line Y-Y′ of FIG. 26, andschematically showing the structure of the limiter unit in the torquefluctuation absorber according to Example 13 of the present disclosure.

DETAILED DESCRIPTION

The inner circumferential end of the conical spring shown byJP2005-127507A (FIG. 2) abuts to one plate, and the outercircumferential end is supported by the other plate. The innercircumferential end of the conical spring contacts with the one plate ata position corresponding to the friction surface of the frictionmaterial against the one plate. Therefore, the conical spring becomeslarge in diameter, increases its cost, resulting in an increased cost ofthe apparatus. Also, since the forming process for the conical spring islong and the spring steel used for conical spring is costly as comparedto general steel material, the cost of the conical spring is increased,resulting in the increased cost of the apparatus. Further, since theinner diameter of the inner circumferential end of the conical spring islarge, and the portion of radially internal of the inner circumferentialend is discarded and yield becomes low, which offers the increased costof the conical spring and also that of the apparatus.

In order to solve the aforementioned problem, various modes are possibleaccording to the present disclosure.

Mode 1 corresponds to the first aspect.

Mode 2

According to the first aspect, the resilient member is preferably aconical spring.

Mode 3

According to the first aspect, the fulcrum point is preferably aforemost part of a protrusion formed on at least one of the second platemember and the fourth plate member.

Mode 4

According to the first aspect, the fulcrum point is preferably anangular part of a step formed on at least one of the second plate memberand the fourth plate member.

Mode 5 corresponds to the second aspect.

Mode 6

In the second aspect, the resilient member is preferably a conicalspring.

Mode 7

In the second aspect, the fourth plate member preferably includes aguide part in an area located radially more inwardly than the second endof the resilient member. The guide part prevents the movement of theresilient member in a direction towards the center of rotation of thefirst rotational shaft.

Mode 8

In the second aspect, the second plate member preferably includes aguide part in an area located radially more outwardly than the first endof the resilient member. The guide part prevents the movement of theresilient member in a direction away from the center of rotation of thefirst rotational shaft.

Mode 9

The torque fluctuation absorber according to the second aspectpreferably includes a flywheel to which the first and fourth platemembers are secured. The fourth plate member abuts against the flywheelin the vicinity of a portion of the fourth plate member abutting againstthe second end of the resilient member.

Mode 10

In the second aspect, the fourth plate member preferably includes a slitor a bend.

Mode 11

The torque fluctuation absorber according to the second aspectpreferably further comprises a flywheel to which the first and fourthplate members are secured. The resilient member may include an abutmentprotruded at the second end. The fourth plate member may include arotation stop non-rotatably and radially non-movably engaged with theabutment. The abutment may abut against the flywheel.

Mode 12 corresponds to the third aspect.

Mode 13

In the third aspect, the sheet spring preferably has one end secured tothe second plate member, while having the other end secured to the firstplate member.

Mode 14

The torque fluctuation absorber according to the third aspect preferablyfurther comprises a fourth plate member arranged at a preset distancefrom the second plate member. The sheet spring has one end secured tothe second plate member, while having the other end secured to thefourth plate member.

Mode 15

In the third aspect, the second plate member preferably has an innerperipheral protrusion. The one end of the sheet spring is secured to theinner peripheral protrusion of the second plate member.

Mode 16

In the third aspect, the sheet spring preferably is a part of the secondplate member. The foremost part of the sheet spring is secured to thefirst plate member.

Mode 17

The torque fluctuation absorber according to the third aspect preferablyfurther comprises a fourth plate member arranged at a preset distancefrom the second plate member. The sheet spring is a part of the secondplate member, and the foremost part of the sheet spring is secured tothe fourth plate member.

Mode 18

The torque fluctuation absorber according to the third aspect preferablyfurther comprises a fourth plate member arranged at a preset distancefrom the second plate member. The second plate member may include anaxially directed protrusion.

The sheet spring may have both ends secured to the fourth plate member.The sheet spring may include a hole engaged by the protrusion of thesecond plate member.

Mode 19

In a fourth aspect, there is provided a torque fluctuation absorber,comprising: a first plate member to which power of rotation istransmitted from a first rotational shaft, a second plate memberarranged at a preset distance from the first plate member, a third platemember arranged between the first and second plate members andconfigured to transmit power of rotation to a second rotational shaft, afourth plate member arranged at a preset distance from the second platemember, and a plurality of resilient members arranged between the secondplate member and the fourth plate member and configured to bias thesecond plate member towards the third plate member. Each of theresilient members has a center axis located in a region where the secondplate member faces the third plate member along the axial direction.

Mode 20

In the fourth aspect, the resilient member preferably is a conicalspring.

Mode 21

In the fourth aspect, the resilient member preferably is a coil spring.

Mode 22

In the fourth aspect, the second plate member or the fourth plate memberpreferably includes a protrusion facing the resilient member. Theprotrusion may be introduced into an inner peripheral part of theresilient member.

Mode 23

In a fifth aspect, there is provided a torque fluctuation absorbercomprising: a first plate member to which power of rotation istransmitted from a first rotational shaft; a second plate memberarranged at a preset distance from the first plate member; a third platemember arranged between the first and second plate members andconfigured to transmit power of rotation to a second rotational shaft;and a fourth plate member arranged at a preset distance from the secondplate member. The torque fluctuation absorber further comprises aresilient member arranged between the second plate member and the fourthplate member and configured to bias the second plate member towards thethird plate member. The resilient member is substantially annular andhas both ends set apart from one another.

Mode 24

In the fifth aspect, the resilient member preferably is formed like asaucer.

Mode 25

In the fifth aspect, both ends of the resilient member preferablyoverlap each other along the circumferential direction.

Mode 26

In the fifth aspect, the resilient member is preferably corrugated alonga circumferential direction and alternately abuts against the secondplate member and the fourth plate member.

Example 1

A torque fluctuation absorber according to Example 1 of the presentdisclosure will now be described with reference to the drawings. FIG. 1depicts a partial radial cross-sectional view schematically showing thestructure of the torque fluctuation absorber according to Example 1 ofthe present disclosure. FIG. 2 depicts an enlarged partial radialcross-sectional view schematically showing the structure of the limiterunit in the torque fluctuation absorber according to Example 1 of thepresent disclosure.

The torque fluctuation absorber 1 according to Example 1 is providede.g. on a power transmission path between an engine side rotationalshaft 6 and a transmission side rotational shaft 7. It is a device forabsorbing (suppressing) the fluctuating torque caused by torsion betweenthe engine side rotational shaft 6 and the transmission gear siderotational shaft 7. The torque fluctuation absorber 1 includes a damperunit 3 having a torsion buffering function and configured for absorbingthe fluctuating torque by spring force (force of resiliency), and ahysteresis unit 4 that absorbs (suppresses) the fluctuating torque bythe hysteresis torque caused e.g. by friction. The torque fluctuationabsorber 1 also includes a limiter unit 2 that generates slip when thetorsion of the rotational shaft has ceased to be absorbed by the damperunit 3 or by the hysteresis unit 4. The damper unit 3 is arranged on thepower transmission path in parallel with the hysteresis unit 4. Thelimiter unit 2 is arranged on the power transmission path in series withthe damper unit 3 and the hysteresis unit 4. The torque fluctuationabsorber 1 may be used, in particular, for a hybrid car having nolimiter unit in the car, and may also be useful for reducing the systemsize in a car not having the limiter unit.

The torque fluctuation absorber includes, as component parts, a flywheel5, a bolt 9, a support plate 10, a cover plate 11, a conical spring 12,a pressure plate 13, a lining plate 14, friction materials 15, 16, sideplates 17, 18, a rivet 19, a coil spring 20 and a seat member 21. Inaddition, the torque fluctuation absorber includes thrust members 22,23, a conical spring 24 and a hub member 25.

The flywheel 5 is an annular plate member fastened by a bolt(s) 8 to theengine side rotational shaft 6. The flywheel 5 has its peripheryprotruded towards the limiter unit 2 to form a cylindrical portion. Thesupport plate 10 and the cover plate 11 are fastened by the bolt(s) 9 tothis cylindrical portion.

The bolt(s) 9 is a member used for fastening the support plate 10 andthe cover plate 11 to the flywheel 5.

The support plate 10 is an annular plate-like member arranged betweenthe flywheel 5 and the cover plate 11, and is a structural part of thelimiter unit 2. The support plate 10 is set at its periphery on thecover plate 11 and the two plates are secured together to the flywheel 5by the bolt 9. The support plate 10 is separated at its inner peripheralpart away from the cover plate 11, and includes a step 10 a protruded atnear its inner peripheral end towards the cover plate 11. The step mayalso be a protrusion. An outer peripheral bent edge of the step 10 aoperates as a fulcrum point 10 b that supports a mid portion of aninclined surface of the conical spring 12 facing an inner peripheralside.

The cover plate 11 is an annular member arranged on the opposite side ofthe flywheel 5 with respect to the support plate 10, viz., on the rightside of FIG. 1, and is a component part of the limiter unit 2. The coverplate 11 is set at its outer peripheral part in contact with the supportplate 10 and the two plates are secured together to the flywheel by thebolt 9. The cover plate 11 has its inner peripheral part separated awayfrom the support plate 10. The cover plate 11 includes a hole(s) 11 afor supporting the pressure plate 13 in such a manner as to preventrelative rotation and to allow for axial movement of the pressure plate13. The pressure plate 13 includes a protrusion 13 a inserted relativelynon-rotatably and axially movably into the hole 11 a. The cover plate 11has a slide surface on its inner peripheral part by which the coverplate is slidably pressed on the friction member 16.

The conical spring 12 is a continuous saucer-shaped spring arrangedbetween the support plate 10 and the pressure plate 13, and is acomponent part of the limiter unit 2. The conical spring 12 biases thepressure plate 13 towards the friction material 15. An inner peripheralend of the conical spring 12 abuts against the pressure plate 13, andthe mid part of an inclined surface of the conical spring 12, facing aninner peripheral side, abuts against the fulcrum point 10 b of the step10 a of the support plate 10. An outer peripheral end of the conicalspring 12 is spaced apart from the support plate 10. The conical spring12 operates for pressuring the pressure plate 13 under assistance by theleverage action about the fulcrum point 10 b. This amplifies the thrustload of the conical spring 12 against the pressure plate 13 to allowreducing the plate thickness of the conical spring 12.

The pressure plate 13 is an annular member arranged between the conicalspring 12 and the friction material 15, and is a component part of thelimiter unit 2. The pressure plate 13 includes a protrusion 13 aoperative to prevent relative rotation and to allow for axial movementof the pressure plate 13 relative to the cover plate 11. The protrusion13 a is introduced through the hole 11 a of the cover plate 11 so thatthe protrusion is unable to perform relative rotation but may performaxial movement. The pressure plate 13 is biased towards the frictionmaterial 15 by the conical spring 12 and is slidably pressed on itsslide surface against the friction material 15.

The lining plate 14 is an annular member arranged between the frictionmaterials 15, 16, which in turn are arranged between the cover plate 11and the pressure plate 13. The lining plate is a component part of thelimiter unit 2. An inner peripheral part of the lining plate 14 issandwiched between the side plates 17 and 18, and is secured to the sideplates 17, 18 by rivet 19. An outer peripheral part of the lining plate14 is secured to the friction materials 15, 16 by a rivet or anadhesive, not shown.

The friction material 15 is a component part of the limiter unit 2, andis arranged between the lining plate 14 and the pressure plate 13. Thefriction material 15 is secured to the lining plate 14 by a rivet or anadhesive, not shown. The friction material 15 is slidably pressed on thepressure plate 13. The friction material 15 used may include rubber,resins, fibers (short fibers or long fibers) or particles for adjustingthe frictional coefficient μ.

The friction material 16 is a component part of the limiter unit 2, andis arranged between the lining plate 14 and the cover plate 11. Thefriction material 16 is secured to the lining plate 14 by a rivet or anadhesive, not shown, and is slidably pressed on the cover plate 11.

The side plate 17 is an annular member arranged on an engine side of aflange part 25 b of the hub member 25, viz., on the left side of FIG. 1,and is a component part of the damper unit 3 and the hysteresis unit 4.The side plate 17 is secured in the vicinity of an outer peripheral partthereof as one to the lining plate 14 and with the side plate 18 by therivet 19. In the damper unit 3, located in an intermediate area, theside plate 17 includes a window 17 a in which a coil spring 20 and aseat member 21 are accommodated. The peripheral end face of the window17 a may be contacted with or separated away from the seat member 21.The side plate 17 is slidably contacted with the first thrust member 22in the hysteresis unit 4 which is located radially more inwardly thanthe damper unit 3. The side plate 17 has its inner peripheral end partcarried by a hub member 25 (hub part 25 a) for relative rotationalmovement via the thrust member 22.

The side plate 18 is an annular member arranged on a transmission sideof the flange part 25 b of the hub member 25, viz., on the right side ofFIG. 1, and is a component part of the damper unit 3 and the hysteresisunit 4. The side plate 18 is secured in the vicinity of an outerperipheral end part thereof by the rivet 19 as one to the liming plate14 and the side plate 17. In the damper unit 3 in an intermediate area,the side plate 18 includes a window 18 a in which the coil spring 20 andthe seat member 21 are accommodated. The peripheral end face of thewindow 18 a may be contacted with or separated away from the seat member21. The side plate 18 carries the conical spring 24 in the hysteresisunit 4 which is located radially more inwardly than the damper unit 2.The side plate 18 has its inner peripheral part carried by the hubmember 25 (hub part 25 a) for relative rotational movement via thethrust member 23.

The rivet 19 is used for securing the liming plate 14, the side plate 17and the side plate 18 together.

The coil spring 20, a component part of the damper unit 3, isaccommodated within the window parts 17 a, 18 a and 25 c, formed in theside plates 17, 18 and in the hub member 25, respectively, and iscontacted with the seat member 21 arranged on both ends. When the sideplates 17, 18 and the hub member 25 perform relative rotationalmovement, the coil spring 20 is contracted to absorb the shock caused bydifferential rotations of the side plates 17, 18 and the hub member 25.The coil spring 20 may be straight-shaped, or may be bent from thestraight shape, with the bent parts being then put together. To allowfor broad torsion, an arc spring, bent along a peripheral direction, mayalso be used.

The seat member 21, a component part of the damper unit 3, isaccommodated within the window parts 17 a, 18 a and 25 c formedrespectively in the side plates 17, 18 and the hub member 25 (flangepart 25 b). The seat member is arranged between the peripheral end facesof the window parts 17 a, 18 a and 25 c and the end of the coil spring20. To reduce the wear caused to the coil spring 20, the seat member 21may be formed of resin.

The thrust member 22, a component part of the hysteresis unit 4, is anannular member arranged between the side plate 17 and the hub member 25.When seen in the axial direction, the thrust member 22 is arrangedbetween the side plate 17 and the flange part 25 b, and is slidablypressed on the side plate 17 and the flange part 25 b. The thrust member22 is also located in the radial direction between the side plate 17 andthe hub part 25 a, and operates as a slide bearing (bush) configured forcarrying the side plate 17 for rotation relative to the hub part 25 a.

The thrust member 23, a component part of the hysteresis unit 4, is anannular member arranged between the side plate 18 and the hub member 25.When seen in the axial direction, the thrust member 23 is arrangedbetween a conical spring 24 and the flange part 25 b, and is biased bythe conical spring 24 towards the flange part 25 b into slidably pressedon the flange part 25 b. When seen in the radial direction, the thrustmember 23 is located between the side plate 18 and the hub member 25 a,and operates as a slide bearing (bush) for carrying the side plate 18for rotation relative to the hub part 25 a.

The conical spring 24, a component part of the hysteresis unit 4, isarranged between the thrust member 23 and the side plate 18. It is asaucer-shaped spring that biases the second thrust member 23 towards theflange part 25 b.

The hub member 25, a component part of the damper unit 3 and thehysteresis unit 4, outputs the power of rotation from the damper unit 3and the hysteresis unit 4 to the transmission. The hub member 25includes the flange part 25 b extended from a preset outer peripheralsite of the hub part 25 a. An inner peripheral side of the hub part 25 ais in splined engagement with the transmission side rotational shaft 7.An outer peripheral part of the hub part 25 a carries the side plate 17for relative rotational movement via the thrust member 22, whilecarrying the side plate 18 for relative rotational movement via thethrust member 23. In the outer peripheral damper unit 3, the flange part25 b includes the window 25 c in which the coil sprig 20 and the seatmember 21 are accommodated. The peripheral end face of the window 25 cis adapted to be contacted with or separated from the seat member 21. Inthe hysteresis unit 4, located more radially inwardly than the damperunit 3, the axially extending surface of the flange part 25 b isslidably sandwiched between the slide members 22, 23.

Meanwhile, FIG. 1 shows a torque fluctuation absorber composed of thedamper unit, hysteresis unit and the limiter unit. The torquefluctuation absorber may, however, include solely the limiter unit.

In Example 1, the thrust load of the conical spring 12 against thepressure plate 13 is amplified by the action of leverage about thefulcrum point 10 b of the support plate 10, and hence the platethickness of the conical spring 12 may be reduced. Hence, the amount ofexpensive spring steel to be in use may be reduced, thus decreasing thecost of the entire device.

Example 2

A torque fluctuation absorber according to Example 2 of the presentdisclosure will now be described with reference to the drawings. FIG. 3depicts an enlarged partial radial cross-sectional view schematicallyshowing the structure of a limiter unit in the torque fluctuationabsorber according to Example 2 of the present disclosure.

Example 2 is a modification of Example 1 (see FIG. 2), in which the step(10 a of FIG. 2) and the fulcrum point (10 b of FIG. 2) are dispensedwith and a fulcrum point for the conical spring 12 is provided on thepressure plate (13 of FIG. 2). An outer peripheral end of the conicalspring 12 abuts against the support plate 10. A mid part of an inclinedsurface of the conical spring 12, facing an outer peripheral side, abutsagainst a circumferential protrusion 13 b of the pressure plate 13. Aninner peripheral end of the conical spring 12 is spaced apart from thepressure plate 13. The circumferential protrusion 13 b is provided at amid part of the pressure plate 13 for extending towards the supportplate 10. The foremost part of the circumferential protrusion 13 b actsas a fulcrum point that supports the mid part of the inclined surface ofthe conical spring 12 facing an outer rim part of the conical spring 12.In other respects, the present Example is similar to Example 1.

In Example 2, the thrust load of the conical spring 12 against thepressure plate 13 may be amplified by the action of leverage about thecircumferential protrusion 13 b of the pressure plate 13, as a fulcrumpoint, thus allowing the plate thickness of the conical spring 12 to bereduced. Hence, the amount of expensive spring steel to be in use may bereduced, thus decreasing the cost of the entire device.

Example 3

A torque fluctuation absorber according to Example 3 of the presentdisclosure will now be described with reference to the drawings. FIG. 4depicts an enlarged partial radial cross-sectional view schematicallyshowing the structure of a limiter unit in a torque fluctuation absorberaccording to Example 3 of the present disclosure. FIG. 5 left and FIG. 5right depict enlarged radial partial cross-sectional views showing thestructure of the limiter unit of the torque fluctuation absorber ofExample 3 of the present disclosure before and after assembling on theflywheel, respectively.

In Example 3, both the diameter and the plate thickness of the conicalspring (12 of FIGS. 2 and 3) are reduced, instead of reducing only itsplate thickness, as in Examples 1 and 2, thereby reducing the cost. Theconical spring 12 has its inner peripheral end abutted against thesupport plate 10, while having its outer peripheral end abutted againstthe pressure plate 13, specifically, against a position in a mid portionof an opposite side surface of the pressure plate having a length equalto the radial length of the friction material 15. The support plate 10is extended radially more inwardly than the inner periphery of theconical spring 12, and includes at its extreme inner peripheral end aguide 10 c protruded towards the pressure plate 13. The guide 10 cprevents the radial movement of the conical spring 12. Before assemblageto the flywheel 5, the support plate 10 has its inner peripheral extremeend tilted towards the flywheel 5. After assemblage of the support plate10 to the flywheel 5, the support plate 10 has its flexure part 10 dflexed so that its inner peripheral extreme end is thrust against aprotrusion 5 a of the flywheel 5 (see FIG. 5). The support plate 10 isprovided with slits or bends to prevent that the flexure part 10 d ofthe support plate is plastically deformed. The protrusion 5 a of theflywheel 5 is provided at a position on an opposite side of the supportplate 10 with respect to the position of abutment of the innerperipheral extreme end of the conical spring 12 against the supportplate. In other respects, the present Example is similar in structure toExample 1.

In Example 3, the outer peripheral extreme end of the conical spring 12abuts against the pressure plate 13, specifically, against a position ina mid portion of an opposite side surface of the pressure plate having alength equal to the radial length of the friction material 15. Hence,the diameter of the conical spring 12 may be reduced. The amount of useof the expensive spring steel material may thus be reduced to lower thecost of the device. Since the diameter of the conical spring 12 isreduced, the thrust load of the conical spring 12 may be increased toallow reducing the plate thickness of the conical spring 12. Since theamount of the expensive spring steel material to be in use may bereduced, the cost of the entire device may be lowered. In addition,since the support plate 10 is thrust against and supported by theflywheel 5 after assemblage thereof to the flywheel 5, it is unnecessaryto increase the strength of the support plate 10. Since the platethickness of the support plate 10 may thus be reduced, the amount of thesteel material may be reduced to lower the cost of the entire device.

Example 4

A torque fluctuation absorber according to Example 4 of the presentdisclosure will now be described with reference to the drawings. FIG. 6depicts an enlarged partial radial cross-sectional view schematicallyshowing the structure of a limiter unit in the torque fluctuationabsorber according to Example 4 of the present disclosure.

The Example 4 is a modification of Example 3 (see FIG. 4). In thepresent Example, the support plate 10 is not thrust against or carriedby the flywheel 5, as in Example 3. Instead, steps 10 e, 10 f areprovided to improve the strength of the support plate 10. The conicalspring 12 has its inner peripheral extreme end abutted against thesupport plate 10, while having its outer peripheral extreme end abuttedagainst the pressure plate 13, specifically, against a position in a midportion of an opposite side surface of the pressure plate having alength equal to the mid portion of the radial length of the frictionmaterial 15. The support plate 10 is extended more radially inwardlythan the conical spring 12, and has a guide 10 c at its inner peripheralextreme end. The guide 10 c is protruded towards the pressure plate 13to prevent radial movement of the conical spring 12. The support plate10 is provided with the steps 10 e, 10 f at its mid portion whichsupports the conical spring 12 and which is thus liable to becomedeformed. The function of the steps 10 e, 10 f is to reduce flexure ofthe support plate 10 in the axial direction. In FIG. 6, the supportplate 10 is provided with the two steps 10 e, 10 f only by way ofillustration. The steps 10 e, 10 f may be arrayed circumferentially inseries, that is, each extending along a radial direction, not only beingarrayed radially in series. The support plate 10 is not provided withslits or bends, as in Example 3. The pressure plate 13 is provided witha circumferentially extending protrusion 13 b which is located radiallymore outwardly than the abutment surface thereof with the outerperipheral extreme end of the conical spring 12. The circumferentiallyprotrusion 13 b prevents radial movement of the conical spring 12. Inother respects, the present Example is similar to Example 1.

In Example 4, the outer peripheral extreme end of the conical spring 12abuts against the pressure plate 13, specifically, against a position ina mid portion of an opposite side surface of the pressure plate having alength equal to the mid portion of the radial length of the frictionmaterial 15. Hence, the diameter of the conical spring 12 may bereduced. Since the amount of the expensive spring steel material to bein use may be reduced, the cost of the entire device may be lowered. Inaddition, since the diameter of the conical spring 12 is reduced, thethrust load of the conical spring 12 may be increased to allow reducingthe plate thickness of the conical spring 12. Since the amount of theexpensive spring steel material to be in use may be reduced, the cost ofthe entire device may be lowered. In addition, since the support plate10 is provided with the steps 10 e, 10 f, the strength of the supportplate 10 may be maintained even if the plate thickness of the supportplate 10 is reduced. Since the amount of steel material may be reduced,the cost of the entire device may be reduced.

Example 5

A torque fluctuation absorber according to Example 5 of the presentdisclosure will now be described with reference to the drawings. FIG. 7depicts an enlarged partial radial cross-sectional view schematicallyshowing the structure of a limiter unit in a torque fluctuation absorberaccording to Example 5 of the present disclosure.

Example 5 is a modification of Example 3 (see FIG. 4). An innerperipheral extreme end of the conical spring 12 is provided with anabutment 12 a. The abutment 12 a rests on the protrusion 5 a of theflywheel 5. The outer peripheral extreme end of the conical spring 12 isabutted against the pressure plate 13. The inner peripheral extreme endof the support plate 10 is provided with a plurality of rotation stops10 g. The conical spring 12 is engaged relatively non-rotatably with therotation stops 10 g of the support plate 10, and is prevented in itsradial movement by these rotation stops 10 g. In other respects, thepresent Example is similar to Example 1.

In the present Example 5, the outer peripheral extreme end of theconical spring 12 is abutted against the pressure plate 13,specifically, against a position in a mid portion of an opposite sidesurface of the pressure plate having a length equal to the radial lengthof the friction material 15. Hence, the diameter of the conical spring12 may be reduced. Since the amount of use of the expensive spring steelmaterial may be reduced, the cost of the device may be lowered.Moreover, since the diameter of the conical spring 12 is reduced, thethrust load of the conical spring 12 may be increased to allow the platethickness of the conical spring 12 to be reduced. Since the amount ofthe expensive spring steel material to be in use may be reduced, thecost of the entire device may be lowered. In addition, since the innerperipheral extreme end of the conical spring 12 (extreme end of therotation stop part 10 a) is supported by the flywheel 5 (protrusion 5a), it is unnecessary to elevate the strength of the support plate 10,and hence the plate thickness of the support plate 10 may be reduced.Since the amount of the steel material used may be reduced, the cost ofthe entire device may be lowered.

Example 6

A torque fluctuation absorber according to Example 6 of the presentdisclosure will now be described with reference to the drawings. FIG. 8depicts an enlarged partial radial cross-sectional view (cross-sectiontaken along lines X-X′ of FIGS. 9 and 10) schematically showing thestructure of a limiter unit in the torque fluctuation absorber accordingto Example 6 of the present disclosure. FIG. 9 depicts an enlargedpartial radial cross-sectional view schematically showing the structureof a pressure plate of the limiter unit in the torque fluctuationabsorber according to Example 6 of the present disclosure. FIG. 10depicts an enlarged partial radial cross-sectional view (cross-sectiontaken along lines Y-Y′ of FIGS. 8 and 9) schematically showing thestructure of the limiter unit in the torque fluctuation absorberaccording to Example 6 of the present disclosure. FIG. 11 depicts anenlarged partial radial cross-sectional view schematically showing thestructure of the limiter unit in the torque fluctuation absorberaccording to Example 6 of the present disclosure.

In Example 6, the conical spring 12, used in Examples 1 to 5, is notused. Instead, a less expensive sheet spring 27 is used. Also, inExample 6, the support plate (10 of FIG. 2) is not used and, instead,the sheet spring 27 is coupled by rivets 28, 29 to the pressure plate 13and to the cover plate 11, respectively. Otherwise, the present Exampleis similar to Example 1.

The cover plate 11 is an annular member fastened by the bolt 9 to theflywheel 5, and is a component part of the limiter unit 2. An innerperipheral part of the cover plate 11 is spaced apart from the supportplate 10. The cover plate 11 includes an inner peripheral slide surfaceby which it is slidably pressed on the friction material 16. The coverplate 11 is fastened by rivet 29 to the sheet spring 27 at a portionbetween the site of the cover plate 11 fastened by the bolt 9 and theslide surface thereof against the friction material 16.

The pressure plate 13 is an annular member slidably pressed on thefriction material 15, and is a component member of the limiter unit 2.The pressure plate 13 is provided with an outer peripheral protrusion 13c at a preset position(s) on its outer peripheral extreme end (see FIG.9). The sheet spring 27 is fastened by rivet 28 to the outer peripheralprotrusion 13 c. The pressure plate 13 is biased by the sheet spring 27towards the friction material 15.

The sheet spring 27 is arranged between the cover plate 11 and the outerperipheral protrusion 13 c of the pressure plate 13, and is a componentpart of the limiter unit 12. The sheet spring 27 biases the pressureplate 13 towards the friction material 15. The sheet spring 27 isextended in the circumferential direction (see FIG. 9) with its midportion traversing the outer periphery of the lining plate 14 and thefriction materials 15, 16 at a spaced apart relation therefrom (see FIG.10). The sheet spring 27 has its one end secured by rivet 28 to theouter peripheral protrusion 13 c of the pressure plate 13, while havingits other end secured by rivet 29 to the cover plate 11.

The rivet 28 is a member that secures the one end of the sheet spring 27to the outer peripheral protrusion 13 c of the pressure plate 13.

The rivet 29 is a member that secures the other end of the sheet spring27 to the cover plate 11.

In FIGS. 8 to 10, the other end of the sheet spring 27 is secured to thecover plate 11. It is however also possible to provide the support plate10 between the flywheel 5 and the cover plate 11 and to connect thesheet spring 27 via the rivets 28, 29 to the pressure plate 13 and tothe support plate 10, as shown in FIG. 11.

In Example 6, in which the sheet spring 27, higher in yield than aconical spring 12, is used, the entire device may be lowered in cost.Moreover, since the sheet spring 27 has the torque transmittingfunction, a rotation stop mechanism that halts rotation of the pressureplate 13 relative to the cover plate 11 (protrusion 13 a and the hole 11a of FIG. 2) may be dispensed with, thereby reducing the cost and thespace. If the support plate (10 of FIG. 11) is not used, as in FIGS. 8to 10, the number of component parts may be reduced to further reducethe cost.

Example 7

A torque fluctuation absorber according to Example 7 of the presentdisclosure will now be described with reference to the drawings. FIG. 12depicts an enlarged partial radial cross-sectional view (cross-sectiontaken along lines X-X′ of FIGS. 13 and 14) schematically showing thestructure of a limiter unit in the torque fluctuation absorber accordingto Example 7 of the present disclosure. FIG. 13 depicts a plan viewschematically showing the structure of a pressure plate of the limiterunit in the torque fluctuation absorber according to Example 7. FIG. 14depicts an enlarged partial radial cross-sectional view (cross-sectiontaken along lines Y-Y′ of FIGS. 12 and 13) schematically showing thestructure of the limiter unit in the torque fluctuation absorberaccording to Example 7.

Example 7 is a modification of Example 6 (see FIGS. 8 to 10). In thepresent Example 7, the sheet spring (27 of FIG. 9) and the rivet (28 ofFIG. 9) in Example 6 are unified to the pressure plate 13. In otherrespects, the present Example is similar to Example 6.

The pressure plate 13 is a member slidably pressed on the frictionmaterial 15, and is a component member of the limiter unit 2. Thepressure plate 13 includes a plurality of the outer peripheralprotrusions 13 c at preset outer peripheral positions (see FIG. 13).Each outer peripheral protrusion 13 c includes a circumferentialextension 13 d along its outer periphery. The circumferential extension13 d acts as a sheet (plate) spring to bias the main part of thepressure plate 13 towards the friction material 15. The circumferentialextension 13 d traverses the outer periphery of the liming plate 14 andthe friction materials 15, 16 at a spaced apart relation therefrom (seeFIG. 14), and has its foremost part secured to the cover plate 11 by therivet 29.

In FIGS. 12 to 14, the foremost part of the circumferential extension 13d of the pressure plate 13 is secured to the cover plate 11. It ishowever also possible to provide the support plate 10 between theflywheel 5 and the cover plate 11, and to connect the foremost part ofthe circumferential extension 13 d of the pressure plate 13 to thesupport plate 10.

In the present Example 7, in which the pressure plate 13 has thefunction of the sheet spring, it is possible to reduce the number ofcomponent parts and hence the cost. Moreover, since the circumferentialextension 13 d of the pressure plate 13 has the torque transmittingfunction, the rotation stop system of halting the rotation of thepressure plate 13 with respect to the cover plate 11 (protrusion 13 aand the hole 11 a of FIG. 2) may be dispensed with. Hence, the cost aswell as the space may be reduced. If the support plate (10 of FIG. 11)is not used, as in FIGS. 12 to 14, the number of component parts may bereduced to further reduce the cost.

Example 8

A torque fluctuation absorber according to Example 8 of the presentdisclosure will now be described with reference to the drawings. FIG. 15depicts an enlarged partial radial cross-sectional view (cross-sectiontaken along lines X-X′ of FIGS. 16 and 17) schematically showing thestructure of a limiter unit in the torque fluctuation absorber accordingto Example 8 of the present disclosure. FIG. 16 depicts a plan viewschematically showing the structure of a pressure plate of the limiterunit in the torque fluctuation absorber according to Example 8 of thepresent disclosure. FIG. 17 depicts an enlarged partial radialcross-sectional view (cross-section taken along lines Y-Y′ of FIGS. 15and 16) schematically showing the structure of the limiter unit in thetorque fluctuation absorber according to Example 8.

Example 8 is a modification of Example 6 (modification shown in FIG.11). In the present Example, the sheet spring 27 is connected to thepressure plate 13 at a location located radially more inwardly than theslide surface of the pressure plate 13 with respect to the frictionmaterial 15. In other respects, the present Example is similar toExample 6 (modification).

The pressure plate 13 is an annular member slidably pressed on thefriction material 15, and is a component part of the limiter unit 2. Thepressure plate 13 includes a plurality of inner peripheral protrusions13 e at preset inner peripheral end positions (see FIG. 16). These innerperipheral protrusions 13 e are secured by rivets 28 to the sheet spring27. The pressure plate 13 is biased by the sheet spring 27 towards thefriction material 15.

The sheet spring 27 is provided between the support plate 10 and theouter peripheral protrusion 13 c of the pressure plate 13, and is acomponent part of the limiter unit 2. The sheet spring 27 biases thepressure plate 13 towards the friction material 15. A mid area of thesheet spring 27 traverses the outer rim of the pressure plate 13 (seeFIG. 16) in a spaced apart relationship therefrom (see FIG. 17). Thesheet spring 27 has its one end secured by the rivet 28 to the innerperipheral protrusion 13 e of the pressure plate 13, while having itsother end secured by the rivet 29 to a surface of the support plate 10facing the cover plate 11.

In Example 8, in which the sheet spring 27, higher in yield than aconical spring 12, is used, the entire device may be lowered in cost.Moreover, since the sheet spring 27 has a torque transmitting function,the rotation stop mechanism that halts the rotation of the pressureplate 13 relative to the cover plate 11 (protrusion 13 a and the hole 11a of FIG. 2) may be dispensed with, thereby reducing the cost and thespace. In addition, the site of connection of the sheet spring 27 to thepressure plate 13 is located radially more inwardly than the slidesurface of the pressure plate 13 relative to the friction material 15,and hence the pressure plate 13 may be reduced in diameter. The amountof steel material to be in use may thus be reduced, thereby furtherreducing the cost and the space.

Example 9

A torque fluctuation absorber according to Example 9 of the presentdisclosure will now be described with reference to the drawings. FIG. 18depicts an enlarged partial radial cross-sectional view (cross-sectiontaken along lines X-X′ of FIGS. 19 and 20) schematically showing thestructure of a limiter unit in the torque fluctuation absorber accordingto Example 9 of the present disclosure. FIG. 19 depicts a plan viewschematically showing the structure of a pressure plate of the limiterunit in the torque fluctuation absorber according to Example 9 of thepresent disclosure. FIG. 20 depicts an enlarged partial radialcross-sectional view (cross-section taken along lines Y-Y′ of FIGS. 18and 19) schematically showing the structure of the limiter unit in thetorque fluctuation absorber according to Example 9.

In Example 9, modified from Example 8 (see FIGS. 15 to 17), no rivet isused for interconnecting the sheet spring 27 and the pressure plate 13.Instead, protrusions 13 f are formed on the pressure plate 13, and ahole 27 a, mating with the protrusion 13 f, is bored in the sheet spring27. The sheet spring 27 is secured by the rivets 29 at two points to thesupport plate 10. The protrusion 13 f of the pressure plate 13 isprojected towards the flywheel 5. The protrusion 13 f is introduced intothe hole 27 a of the sheet spring 27 to prevent its movement in thecircumferential and radial directions is prevented. In other respects,the present Example is similar to Example 8.

In Example 9, in which the sheet spring 27, higher in yield than aconical spring 12, is used, the entire device may be lowered in cost.Moreover, since the sheet spring 27 has a torque transmitting function,a rotation stop unit that halts rotation of the pressure plate 13relative to the cover plate 11 (protrusion 13 a and the hole 11 a ofFIG. 2) may be dispensed with, thereby reducing the cost and the space.In addition, since the sheet spring 27 and the pressure plate 13 areinterconnected by having the protrusion 13 f of the pressure plate 13engaged in the hole 27 a of the sheet spring 27, the pressure plate 13may be reduced in diameter. Hence, the amount of the steel material tobe in use may be reduced, thereby reducing the cost of the device andspace.

Example 10

A torque fluctuation absorber according to Example 10 of the presentdisclosure will now be described with reference to the drawings. FIG. 21depicts an enlarged partial radial cross-sectional view (cross-sectiontaken along line X-X′ of FIG. 22) schematically showing the structure ofa limiter unit in the torque fluctuation absorber according to Example10 of the present disclosure. FIG. 22 is a plan view schematicallyshowing the structure of a pressure plate of the limiter unit of thetorque fluctuation absorber according to Example 10.

In Example 10, modified from Example 1 (see FIG. 2), a plurality ofconical springs 31, each being of a smaller diameter corresponding tothe radial extent of the friction material 15, are used in place of asole conical spring of a larger diameter (12 of FIG. 2) as in Example 1.The pressure plate 13 includes a plurality of protrusions 13 f matingwith holes bored in the inner rim of the conical springs 31. Theprotrusions 13 f prevent the movement of the conical springs 31 in thecircumferential and radial directions. The inner peripheral ends of theconical springs 31 abut against the portions of the pressure plate 13located on the outer periphery of the protrusions 13 f of the pressureplate 13, with the outer peripheral ends of the conical springs 31abutting against the support plate 10. The conical springs 31 bias thepressure plate 13 towards the friction material 15. The center axis ofthe conical spring 31 is located in an area of the portion of thepressure plate 13 axially facing the lining plate 14, viz., within theextent of the radial length of the friction material 15. In otherrespects, the present Example is similar to Example 8.

In FIG. 21, the conical spring 31 has the inner peripheral end abuttedagainst the outer peripheral area of the protrusion 13 f of the pressureplate 13, while having the outer peripheral end abutted against thesupport plate 10. Conversely, the conical spring 31 may also have theouter peripheral end abutted against the outer peripheral area of theprotrusion 13 f of the pressure plate 13, while having the innerperipheral end abutted against the support plate 10. In the latter case,a protrusion like the protrusion 13 f provided on the pressure plate 13is preferably formed on the support plate 10.

In Example 10, in which the multiple conical springs 31 of smallerdiameters are used, the yield of the spring steel material may beimproved, thus reducing the cost of the entire device.

Example 11

A torque fluctuation absorber according to Example 11 of the presentdisclosure will now be described with reference to the drawings. FIG. 23depicts an enlarged partial radial cross-sectional view schematicallyshowing the structure of a limiter unit in the torque fluctuationabsorber according to Example 11 of the present disclosure.

In Example 11, modified from Example 10 (see FIGS. 21 and 22), aplurality of coil springs 32 of smaller diameters are used in place ofthe multiple conical springs of smaller diameters. The pressure plate 13includes a plurality of protrusions 13 f mating with the innerperipheral bores in the coil springs 32. The protrusions 13 f preventcircumferential and radial movements of the coil springs 32. Each coilspring 32 has its one end abutted against the pressure plate 13 in anarea of an outer periphery of the protrusion 13 f of the pressure plate13, while having its outer peripheral end abutted against the supportplate 10. Each coil spring 32 biases the pressure plate 13 towards thefriction material 15. The center axis of the coil spring 32 is locatedwithin the area of axial opposition of the pressure plate 13 to thelining plate 14, that is, within the extent of the radial length of thefriction material 15. In other respects, the Example 11 is similar toExample 10.

In FIG. 23, the protrusions 13 f is provided on the pressure plate 13.The protrusion may, however, be provided on only the support plate 10,or on each of the pressure plate 13 and the support plate 10.

In Example 11, in which the coil springs 32 of smaller diameters areused, the production yield may be improved, thus lowering the cost ofthe entire device.

Example 12

A torque fluctuation absorber according to Example 12 of the presentdisclosure will now be described with reference to the drawings. FIG. 24left depicts an enlarged partial radial cross-sectional viewschematically showing the structure of a conical spring 12 of a limiterunit in the torque fluctuation absorber according to Example 12 of thepresent disclosure, during its preparation, and FIG. 24 right depicts asimilar enlarged partial radial cross-sectional view schematicallyshowing the structure of the conical spring after completion. FIG. 25depicts an enlarged partial radial cross-sectional view schematicallyshowing the structure of a modification of the conical spring 12 of thelimiter unit in the torque fluctuation absorber according to Example 12of the present disclosure.

In Example 12, modified from the conical spring 12 of Example 1 (12 ofFIG. 2), a conical spring 33, composed of a plain sheet-shaped steelmaterial, is bent to form an annular conical shape for use in place ofthe non-interrupted conical spring (12 of FIG. 2) of Example 1. The endsof the conical spring 33 are not joined together (i.e., forming freeends with or/without a gap). As in Example 1, the inner peripheral endof the conical spring 33 abuts against the pressure plate (13 of FIG.2). A mid part of an inclined surface of the conical spring 33, facingan inner rim side, abuts against the fulcrum point (10 b of FIG. 2) ofthe step (10 a of FIG. 2) of the support plate (10 of FIG. 2), with theouter rim side end of the conical spring being spaced apart from thesupport plate (10 of FIG. 2). The conical spring 33 biases the pressureplate 13 towards the friction material 15. Meanwhile, bothcircumferential ends of the conical spring 33 may overlap with eachother (see FIG. 25).

In Example 12, in which the conical spring 33, the ends of which are notjoined to each other, is used, the yield of the spring steel materialmay be improved, thus reducing the cost. In addition, if both ends ofthe conical spring 33 are overlapped together, the load may be made evento allow a larger load to be produced.

Example 13

A torque fluctuation absorber according to Example 13 of the presentdisclosure will now be described with reference to the drawings. FIG. 26depicts an enlarged partial radial cross-sectional view (cross-sectiontaken along line X-X′ of FIG. 27) schematically showing the structure ofa limiter unit in the torque fluctuation absorber according to Example13 of the present disclosure. FIG. 27 depicts a similar enlarged partialradial cross-sectional view (cross-section taken along line Y-Y′ of FIG.26) schematically showing the structure of the limiter unit in thetorque fluctuation absorber according to Example 13.

FIG. 13, modified from Example 1, uses a corrugated spring 34 in placeof using a non-interrupted conical spring of Example 1 (12 of FIG. 2).The corrugated spring 34 is obtained on forming a plane sheet-shapedspring steel material into an annular corrugated shape. The extreme endsof the corrugated spring 34 are not joined together. The corrugatedspring 34 alternately abuts against the pressure plate 13 and thesupport plate 10. The portions of the corrugated spring 34 not abuttingagainst the pressure plate 13 or the support plate 10 operate as a sheetspring. The corrugated spring 34 biases the pressure plate 13 towardsthe friction material 15. It is noted that, to prevent circumferentialas well as radial movement of the corrugated spring 34, the corrugatedspring 34 may be secured by a rivet, not shown, to the support plate 10,while the support plate 10 may be provided with the guide 10 c shown inFIG. 4. In other respects, the Example 11 is similar to Example 10.

In Example 13, in which the corrugated spring 34, whose extreme ends arenot joined together, is used, the spring steel material may be improvedin yield, while the cost of the entire product may be lowered. Moreover,the corrugated spring 34 is easier in forming than the conical spring.

The particular exemplary embodiments or examples may be modified oradjusted within the gamut of the entire disclosure of the presentdisclosure, inclusive of claims, based on the fundamental technicalconcept of the disclosure. Further, variegated combinations orselections of elements disclosed herein may be made within the scope ofthe claims. That is, the present disclosure may encompass variousmodifications or corrections that may occur to those skilled in the artin accordance with and within the gamut of the entire disclosurethereof, inclusive of claim and the technical concept of the presentdisclosure.

EXPLANATION OF NUMERALS

-   1 torque fluctuation absorber-   2 limiter unit-   3 damper unit-   4 hysteresis unit-   5 flywheel-   5 a protrusion-   6 engine side rotational shaft (first rotational shaft)-   7 transmission side rotational shaft (second rotational shaft)-   8, 9 bolts-   10 support plate (fourth plate member)-   10 a step-   10 b fulcrum point-   10 c guide-   10 d flexure part-   10 e, 10 f steps-   10 g rotation stop-   11 cover plate (first plate member)-   11 a hole-   12 conical spring (resilient member)-   12 a abutment-   13 pressure plate (second plate member)-   13 a protrusion-   13 b circumferential protrusion (fulcrum point and guide part)-   13 c outer peripheral protrusion-   13 d circumferential extension-   13 e inner peripheral protrusion-   13 f protrusion-   14 lining plate (third plate member)-   15, 16 friction materials-   17 side plate-   17 a window-   18 side plate-   18 a window-   19 rivet-   20 coil spring-   21 seat member-   22, 23 thrust members-   24 conical spring-   25 hub member-   25 a hub part-   25 b flange part-   25 c window-   26 sheet spring-   27 a hole-   28, 29 rivets-   31 conical spring (resilient member)-   32 coil spring-   33 conical spring (resilient member)-   34 corrugated spring (resilient member)

1. A torque fluctuation absorber, comprising: a first plate member towhich power of rotation is transmitted from a first rotational shaft; asecond plate member arranged at a preset distance from the first platemember; a third plate member arranged between the first and second platemembers and configured to transmit power of rotation to a secondrotational shaft; a fourth plate member arranged at a preset distancefrom the second plate member; and a resilient member arranged betweenthe second plate member and the fourth plate member and configured tobias the second plate member towards the third plate member; at leastone of the second plate member and the fourth plate member having afulcrum point supporting a mid portion of the resilient member.
 2. Thetorque fluctuation absorber according to claim 1, wherein the resilientmember is a conical spring.
 3. The torque fluctuation absorber accordingto claim 1, wherein the fulcrum point is a foremost part of a protrusionformed on at least one of the second plate member and the fourth platemember.
 4. The torque fluctuation absorber according to claim 1, whereinthe fulcrum point is a bent edge of a step formed on at least one of thesecond plate member and the fourth plate member.
 5. A torque fluctuationabsorber, comprising: a first plate member to which power of rotation istransmitted from a first rotational shaft; a second plate memberarranged at a preset distance from the first plate member; a third platemember arranged between the first and second plate members andconfigured to transmit power of rotation to a second rotational shaft; afourth plate member arranged at a preset distance from the second platemember; and a resilient member arranged between the second plate memberand the fourth plate member and configured to bias the second platemember towards the third plate member; the resilient member including afirst end located at a position having a preset distance from a centerof rotation of the first rotational shaft and a second end located at aposition more closely to the center of rotation of the first rotationalshaft than the first end; the first end abutting against the secondplate member in an area where the second plate member faces the thirdplate member in the axial direction; the second end abutting against thefourth plate member.
 6. The torque fluctuation absorber according toclaim 5, wherein the resilient member is a conical spring.
 7. The torquefluctuation absorber according to claim 5, wherein the fourth platemember includes a guide part in an area located radially more inwardlythan the second end of the resilient member, and wherein the guide partprevents movement of the resilient member in a direction towards acenter of rotation of the first rotational shaft.
 8. The torquefluctuation absorber according to claim 5, wherein the second platemember includes a guide part in an area located radially more outwardlythan the first end of the resilient member, and wherein the guide partprevents movement of the resilient member in a direction away from thecenter of rotation of the first rotational shaft.
 9. The torquefluctuation absorber according to claim 5, further comprising: aflywheel to which the first and fourth plate members are secured, andwherein the fourth plate member abutting against the flywheel in thevicinity of a portion of the fourth plate member abutting against thesecond end of the resilient member.
 10. The torque fluctuation absorberaccording to claim 9, wherein the fourth plate member includes a slit ora bend.
 11. The torque fluctuation absorber according to claim 5,further comprising: a flywheel to which the first and fourth platemembers are secured, wherein the resilient member includes an abutmentprotruded at the second end, wherein the fourth plate member includes arotation stop non-rotatably and radially non-movably engaged with theabutment, and wherein the abutment abuts against the flywheel.
 12. Atorque fluctuation absorber comprising: a first plate member to whichthe power of rotation is transmitted from a first rotational shaft; asecond plate member arranged at a preset distance from the first platemember; a third plate member arranged between the first and second platemembers and configured to transmit power of rotation to a secondrotational shaft; and a sheet spring biasing the second plate membertowards the third plate member.
 13. The torque fluctuation absorberaccording to claim 12, wherein the sheet spring has one end secured tothe second plate member and the other end secured to the first platemember.
 14. The torque fluctuation absorber according to claim 12,further comprising: a fourth plate member arranged at a preset distancefrom the second plate member and wherein; the sheet spring has one endsecured to the second plate member and the other end secured to thefourth plate member.
 15. The torque fluctuation absorber according toclaim 14, wherein the second plate member has an inner peripheralprotrusion, and wherein the one end of the sheet spring is secured tothe inner peripheral protrusion of the second plate member.
 16. Thetorque fluctuation absorber according to claim 12, wherein the sheetspring is a part of the second plate member, and wherein the foremostpart of the sheet spring is secured to the first plate member.
 17. Thetorque fluctuation absorber according to claim 12, further comprising: afourth plate member arranged at a preset distance from the second platemember, wherein the sheet spring is a part of the second plate member,wherein the foremost part of the plate spring is secured to the fourthplate member.
 18. The torque fluctuation absorber according to claim 12,further comprising: a fourth plate member arranged at a preset distancefrom the second plate member, wherein the second plate member includesan axially directed protrusion, wherein the sheet spring has both endssecured to the fourth plate member, and wherein the sheet springincludes a hole engaged by the protrusion of the second plate member.